At least 13 workers have died after a fire broke out at a suspected illegal garment factory on the outskirts of Delhi in India on Friday morning. Local police spokesperson Bhagwat Singh told AFP that the workers were sleeping when the blaze took hold on the ground floor of the narrow residential building, which was being used to make faux-leather jackets in the suburb of Sahibabad. Authorities believe that the fire, which started at 4:30 a.m. local time, is the result of either faulty wiring or a unextinguished cigarette. Police superintendent Salman Taj said that three of the 13 were burned to death; the others succumbed to smoke inhalation. Another two to three workers, whom witnesses said survived by leaping from the building’s balcony, were rushed to the hospital, where they’re being treated for injuries.

“From what we see, there was nothing proper and the factory must surely not have been a legal one but we can say for sure only after a proper investigation,” he said.

Residents described the neighborhood as a hub of illegal factories that employed mostly underpaid migrant workers.

Unregulated factories are a problem for the garment industry. Typically subcontracted—or even sub-sub-contracted—by “first-tier” factories, often without the knowledge of the commissioning brands or retailers, most of these “shadow” facilities lack basic safety measures such as emergency exits and extinguishers, let alone any kind of reasonable oversight.

The opaque and convoluted nature of these networks have complicated attempts to reform the garment industry in the wake of the collapse of the multi-factory Rana Plaza building, which killed 1,138 people, and injured thousands more, in Bangladesh in April 2013.